Axe asa is leaking PLEASE HELP

Bottom of empire axe asa has had a leak where the handle is. It still shoots fine and doesnt really bother the efficiency but its very annoying. Ive had my gun tuned and it is at about 165. In the manual it said to turn a plug cap on reg because its probably the release valve but i dont know what it looks like. please post pictures or describe what it looks like thanks.